1. Field of the Invention
The ability to measure events, the presence of specific materials, and rates of reaction; the detection of disease states; the increase in sensitivity of measurements, and the like, has undergone enormous elaboration in the variety of techniques, protocols, and materials used. The ability to measure a specific compound, mixture of compounds, aggregation or complex unit in a medium is of interest to such diverse applications as process monitoring, pollutants in air and water, drug determinations in physiological fluids, disease diagnosis, histocompatibility between individuals, food quality and the like. Concentrations of interest may vary from molar to picomolar or less.
Because of the wide diversity of materials of interest, environments in which measurements are to be made, variations in sensitivity, as well as the information desired, numerous reagents, devices and protocols have been developed having varying degrees of specificity, modes of application, sophistication and complexity. Nevertheless, there still remains opportunities for new devices employing novel protocols, which can be used as rapid sensitive detection methods to determine changes in an environment, the presence of a particular substance or group or aggregation of substances, or the like.
There is also an interest in being able to control spatial relationships between diverse compositions. The capability of defining spatial relationships between compositions would be of significant importance in understanding molecular interactions, providing for novel processes and performing specific manipulations at molecular levels.
2. Description of the Prior Art
Representative literature disclosures of such processes and the electroanalytical elements they employ include for example, FEBS Letters Vol. 109, No. 2 (January 1980) pages 252-6 entitled "Some Different Ways to use Adsorption of Molecules on Electrodes to Measure Enzymatic Activity" by Arwin and Lundstrom; Journal of Colloid and Interface Science Vol. 72, No. 2 (November 1979) pages 255-264 entitled "Silicon-Silicon Dioxide as an Electrode for Electrical and Ellipsometric Measurements of Adsorbed Organic Molecules" by Stenberg, Arwin and Nilsson; Med. and Biol. Eng. and Compt., 1979, 17, 647-654, entitled "From Conventional Membrane Electrodes to Ion-sensitive Field-effect Transistors" by Bergveld and de Rooij; IEEE Trans BMI-23, (1976), pages 136-144, entitled "Extracellular Potential Recordings by Means of a Field Effect Transistor Without Gate Metal, Called OSFET" by Bergveld, Wiersma and Meertens; Surface Science 86 (1979) pages 322-334 entitled "Chemically Sensitive Devices" by Zemel; IEEE Transactions on Electron Devices Vol. ED-26, No. 12, (December 1979), pages 1959-1964, entitled "The Si.sub.3 N.sub.4 /Si Ion-Sensitive Semiconductor Electrode" by Lauks and Zemel; and Composant Biomedical Vol. 57, (1977) pages 451-454 entitled "Ion-Sensitive Field Effect Transistor" by Bergveld.
Patent disclosures concerning this subject include, for example, U.S. Pat. No. 3,966,580 of Janata et al.,; U.S. Pat. No. 3,799,743 of Alexander et al.; U.S. Pat. No. 4,072,576 of Arwin et al.; U.S. Pat. No. 4,020,830 of Johnson; and U.S. Pat. No. 4,321,123 of Nakamura et al.